Fischer-tropsch gasoil fraction

ABSTRACT

The present invention provides a Fischer-Tropsch gasoil fraction having an initial boiling point of at least 175° C. and a final boiling point of at most 285° C. In another aspect the present invention provides a fuel composition and the use of a Fischer-Tropsch gasoil fraction according to the invention.

The present invention relates to a Fischer-Tropsch gasoil fraction, fuel compositions comprising the Fischer-Tropsch gasoil fraction, and use of the Fischer-Tropsch gasoil fraction.

Hydrocarbon gasoils may be crude oil derived in nature or be synthetically-derived. GB2503988 discloses a synthetic gasoil derived from an olefin oligomerisation process. Currently, Fischer-Tropsch derived gasoils receive significant commercial attention. Fischer-Tropsch derived gasoils may be obtained by various processes. A Fischer-Tropsch derived gasoil is obtained using the so-called Fischer-Tropsch process. A Fischer-Tropsch process produces a range of hydrocarbon products, including naphtha, gasoil, kerosene, base oil and other products. US2008/0250704 discloses a highly isoparaffinic Fischer-Tropsch kerosene containing less than 10% of paraffins. The gasoil product is also referred to as the full-range Fischer-Tropsch derived gasoil. An example of such process producing a Fischer-Tropsch derived gasoil is disclosed in WO 02/070628.

In U.S. Pat. No. 5,906,727, a Fischer-Tropsch derived solvent based on a full-range Fischer-Tropsch derived gasoil is disclosed with a boiling range from approximately 160 to 370° C.

In US2010/0307428 discloses a full-range Fischer-Tropsch derived gasoil with a boiling range from approximately 130 to 370° C.

There is a need in the art for Fischer-Tropsch derived gasoils fractions that have a more narrow boiling point range compared to the solvent disclosed in U.S. Pat. No. 5,906,727.

It has now surprisingly been found that specific Fischer-Tropsch gasoil fractions of the full-range Fischer-Tropsch derived gasoil can be advantageously used in heating oil, lamp oil and lighter fluid applications.

To this end, the present invention provides a Fischer-Tropsch gasoil fraction having an initial boiling point of at least 175° C. and a final boiling point of at most 285° C.

An advantage of the present invention is that the Fischer-Tropsch gasoil fraction has surprisingly a low viscosity while having a high flash point, which combination of properties provides advantages in heating oil, lamp oil and lighter fluid applications.

Typically, the Fischer-Tropsch gasoil fraction according to the present invention has very low levels of aromatics, naphthenic paraffins (also referred to as naphthenics) and impurities. In particular the low level of impurities, aromatics and naphthenic paraffins has the advantage that in heating oil, lamp oil and lighter fluid applications, the fraction exhibits low sooting and smoke formation and low odour during burning and extinguishing, as well as a low odor of the fraction itself.

The Fischer-Tropsch gasoil fraction according to the present invention is a fraction of the full-range Fischer-Tropsch gasoil that is derived from a Fischer-Tropsch process. Full-range Fischer-Tropsch derived gasoil, herein also referred to as Fischer-Tropsch gasoil, is known in the art. By the term “Fischer-Tropsch derived” is meant that the gasoil, is, or is derived from, a synthesis product of a Fischer-Tropsch process. In a Fischer-Tropsch process, synthesis gas is converted to a synthesis product. Synthesis gas or syngas is a mixture of predominantly hydrogen and carbon monoxide that is obtained by conversion of a hydrocarbonaceous feedstock. Suitable feedstocks include natural gas, crude oil, heavy oil fractions, coal, biomass or lignocellulosic biomass and lignite. A Fischer-Tropsch derived gasoil may also be referred to as a GTL (Gas-to-Liquids) gasoil. The Fischer-Tropsch gasoil is characterized as the product of a Fischer-Tropsch process wherein a synthesis gas, or mixture of predominantly hydrogen and carbon monoxide, is processed at elevated temperature over a supported catalyst comprised of a Group VIII metal, or metals, e.g., cobalt, ruthenium, iron, etc. At least part of the Fischer-Tropsch product is contacted with hydrogen, at hydrocracking/hydroisomerization conditions over a, preferably, bifunctional, catalyst, or catalyst containing a metal, or metals, hydrogenation component and an acidic oxide support component active in producing both hydrocracking and hydroisomerization reactions. A least part of the resulting hydrocracked/hydroisomerized Fischer-Tropsch product may be provided as the Fischer-Tropsch derived gasoil feedstock.

Fischer-Tropsch gasoils are different from crude oil-derived gasoils. Despite having a similar boiling point range, the specific molecular composition of the Fischer-Tropsch gasoils may allow for, amongst others, improved viscosity characteristics, improved pour point characteristics, improved density characteristics and in particular a combination of any of the aforementioned characteristics with specific desired flash point characteristics. For example, Fischer-Tropsch gasoils may combine a low volatility with a high flash point, whereas the viscosity of such Fischer-Tropsch gasoils may be lower than the viscosity of crude oil-derived gasoil feedstock having a similar volatility and flash point.

The different characteristics of the Fischer-Tropsch gasoils, compared to the crude oil-derived gasoils, are generally attributed to their particular isoparaffin to normal paraffin weight ratio (i/n ratio), relative amount of mono-methyl branched isoparaffins (mono-methyl isoparaffins) and the molecular weight distribution of the paraffins.

A particular advantage of the Fischer-Tropsch derived gasoils is that these gasoils are almost colorless. Color as used herein is the Saybolt color as measured by its Saybolt number (ASTM D156: Standard Test Method for Saybolt Color of Petroleum Products). A high Saybolt number, +30, indicates colorless fluids, whereas lower Saybolt numbers, in particular below zero, indicate a discoloration. A Saybolt number lower than 25 already indicates the presence of a visually observable discoloration. Fischer-Tropsch gasoils typically have the highest Saybolt number, i.e. +30. The good color characteristics, together with the above mentioned improved viscosity, pour point, density and flash point characteristics make the Fischer-Tropsch derived gasoils highly suitable for heating oil, lamp oil and lighter fluid applications.

It has now been found that it may be possible to meet specific requirements of particular applications of the Fischer-Tropsch derived gasoil by using a specific fraction of a Fischer-Tropsch gasoil, wherein the fraction has a more narrow boiling point range compared to the full-range Fischer-Tropsch gasoil. By fractionating the Fischer-Tropsch gasoil, isoparaffins and normal paraffins are distributed unevenly over the fractions and Fischer-Tropsch gasoil fractions may be obtained that have an i/n ratio different from the original Fischer-Tropsch gasoil. Also the relative amount of mono-methyl branched isoparaffins and the molecular weight distribution of the paraffins may be different. As a consequence the viscosity, pour point, density and flash point characteristics of the Fischer-Tropsch gasoil fractions may be changed, beyond the change that would be expected on the basis of a fractionation on the basis of boiling ranges alone. Fischer-Tropsch gasoils contain primarily isoparaffins, however they also contain normal paraffins. Preferably, the Fischer-Tropsch gasoil fraction comprises more than 65 wt %, more preferably more than 70 wt % of isoparaffins.

A fraction of the Fischer Tropsch gasoil is a narrower boiling range distillation cut of the Fischer Tropsch gasoil.

According to the present invention, the Fischer-Tropsch gasoil fraction has an initial boiling point of at least 175° C. and a final boiling point of at most 285° C., at atmospheric conditions. Suitably, the Fischer-Tropsch gasoil fraction has an initial boiling point of at least 180° C., more preferably at least 188° C., at atmospheric conditions.

The Fischer-Tropsch gasoil fraction preferably has a final boiling point of at most 280° C., at atmospheric conditions. Further, the Fischer-Tropsch gasoil fraction preferably has a final boiling point of at most 278° C., at atmospheric conditions. By excluding higher boiling hydrocarbons that normally considered to be part of a full-range Fischer-Tropsch gasoil, less fouling in burners may be generated, while overall improved burning properties may be obtained.

A preferred Fischer-Tropsch gasoil fraction has an initial boiling point of at least 180° C., and a final boiling point of at most 280° C., at atmospheric conditions. A more preferred Fischer-Tropsch gasoil fraction has an initial boiling point of at least 188° C. and a final boiling point of at most 278° C., at atmospheric conditions

By boiling points at atmospheric conditions is meant atmospheric boiling points, which boiling points are determined by ASTM D86.

Preferably, the Fischer-Tropsch gasoil fraction has a T10 vol % boiling point in the range of from 198 to 216° C., more preferably of from 201 to 213° C., most preferably from of 204 to 210° C. and a T90 vol % boiling point in the range of from 250 to 268° C., preferably of from 253 to 265° C. and more preferably of from 256 to 262° C.

T10 vol % boiling point is the temperature corresponding to the atmospheric boiling point at which a cumulative amount of 10 vol % of the product is recovered. Similarly, T90 vol % boiling point is the temperature corresponding to the atmospheric boiling point at which a cumulative amount of 90vol % of the product is recovered. The atmospheric distillation method ASTM D86 is used to determine the level of recovery.

The Fischer-Tropsch gasoil fraction comprises preferably paraffins having from 9 to 19 carbon atoms; the Fischer-Tropsch paraffin gasoil fraction comprises preferably at least 70 wt %, more preferably at least 85 wt %, more preferably at least 90 wt %, more preferably at least 95 wt %, and most preferably at least 98 wt % of Fischer-Tropsch paraffins having 9 to 19 carbon atoms based on the total amount of Fischer-Tropsch paraffins.

Further, the Fischer-Tropsch gasoil fraction preferably has a density at 15° C. according to ASTM D4052 in the range of from 762 kg/m³ to 768 kg/m³, more preferably of from 763 kg/m³ to 767 kg/m³, and most preferably from 764 kg/m³ to 766 kg/m³.

Suitably, the kinematic viscosity at 25° C. according to ASTM D445 is in the range of from 2.2 to 2.8 cSt, preferably of from 2.3 cSt to 2.7 cSt, and more preferably of from 2.4 cSt to 2.6 cSt.

Preferably, the Fischer-Tropsch gasoil fraction has a flash point according to ASTM D93 of at least 67° C., preferably in the range of from 67 to 81° C., more preferably of from 70 to 78° C., and most preferably of from 71 to 77° C.

The Fischer-Tropsch gasoil fraction has a smoke point according to ASTM D1322 of more than 50 mm.

Typically, the Fischer-Tropsch gasoil fraction according to the present invention comprises less than 500 ppm aromatics, preferably less than 360 ppm aromatics, more preferably less than 300 ppm aromatics, less than 3 ppm sulphur, preferably less than 1 ppm sulphur, more preferably less than 0.2 ppm sulphur, less than 1 ppm nitrogen and less than 4 wt % naphthenics, preferably less than 3 wt % and more preferably less than 2.5 wt % naphthenics.

Further, the Fischer-Tropsch gasoil fraction preferably comprises less than 0.1 wt % polycyclic aromatic hydrocarbons, more preferably less than 25 ppm polycyclic aromatic hydrocarbons and most preferably less than 1 ppm polycyclic aromatic hydrocarbons.

The amount of isoparaffins is suitably more than 65 wt % based on the total amount of paraffins having in the range of from 9 to 19 carbon atoms, preferably more than 70 wt %.

Further, the Fischer-Tropsch gasoil fraction may comprise normal paraffins, also referred to as n-paraffins, and cyclo-alkanes.

The Fischer-Tropsch gasoil fraction preferably has an isoparaffin to normal paraffin weight ratio (also referred to as i/n ratio) of in the range of from 2.5 to 3.5. This relatively high i/n ratio may advantageously affect amongst others the viscosity of the Fischer-Tropsch gasoil fraction. The relative high concentration of isoparaffin may provide a lower overall viscosity of a Fischer-Tropsch gasoil.

Preferably, the Fischer-Tropsch gasoil fraction comprises in the range of from 35 to 55 wt %, more preferably of from 45 to 55 wt %, of mono-methyl branched isoparaffins, based on the total weight of isoparaffins in the Fischer-Tropsch gasoil fraction. Mono-methyl branched isoparaffins exhibit desirable bio degradation characteristic compared to other isoparaffins. A relative high concentration of mono-methyl isoparaffins to other isoparaffins may advantageously affect amongst others the bio degradation characteristics of the Fischer-Tropsch gasoil fractions. A higher relative concentration of mono-methyl isoparaffin to other isoparaffins may provide the Fischer-Tropsch gasoil fraction with bio degradation characteristics beyond the bio degradation characteristics of the Fischer-Tropsch gasoil.

The Fischer-Tropsch gasoil fraction has a much narrower boiling range compared to the Fischer-Tropsch gasoil, allowing for its use in many applications. Due to its relative highly paraffinic nature and relative low levels of naphthenic and aromatic components and in addition the relative low levels of impurities, the Fischer-Tropsch gasoil fraction of the invention incorporates several technical benefits over conventional, crude oil derived fluids. Compared to existing isoparaffinic fluids currently on the market, the Fischer-Tropsch gasoil fraction has a more desirable mix of isoparaffins and n-paraffins. While competitive isoparaffinic fluids predominantly contain isoparaffins, and especially the higher boiling isoparaffins, including naphthenic paraffins, this Fischer-Tropsch gasoil fraction of the invention contains isoparaffins and n-paraffins, while containing very minor amounts of naphthenic paraffins.

When used in for instance heating oil, lamp oil or lighter fluid applications a high flash point is desirable for safety reasons. Where prior art gasoils used for these applications suffered from an undesired high viscosity when using a high flash point gasoil, the Fischer-Tropsch gasoil fraction of the present invention having its specific composition and branching provides a high flash point while remaining a viscosity that is relatively low compared to prior art isoparaffinic fluids, at same flash point levels. The combination of having a low viscosity and at the same time a relatively high flash point may find its benefits in heating oil, lamp oil, and lighter fluid applications by increasing safety, improving burning characteristics and causing less fouling in electronically regulated home heating devices.

The preparation of the Fischer-Tropsch gasoil feedstock used as a basis for the Fischer-Tropsch gasoil fraction of the present invention has been described in e.g. WO02/070628 and WO-A-9934917 (in particular the process as described in Example VII of WO-A-9934917, using the catalyst of Example III of WO-A-9934917), both of which are hereby incorporated by reference. As mentioned above these Fischer-Tropsch derived gasoil feedstocks have a different molecular composition and have significantly different properties compared to crude oil-derived gasoil feedstock. Therefore, Fischer-Tropsch derived gasoil feedstocks can be clearly distinguished from crude oil-derived gasoil feedstocks.

In a further aspect, the present invention provides a fuel composition comprising a Fischer-Tropsch gasoil fraction according the invention. One particularly preferred fuel composition is a heating oil. Heating oils herein are fuel composition s used for domestic heating purposes. Another particularly preferred fuel composition is a lamp oil. Lamp oils herein are fuel compositions typically used for domestic illumination purposes, for instance using an oil lamp, sometimes in combination with a fragrance, perfume, or insect repellent. A further particularly preferred fuel composition is a lighter fluid, in particular barbeque lighter fluids.

The Fischer-Tropsch gasoil fraction may be used in combination with other compounds in the composition. Other compounds that are used in combination with the Fischer-Tropsch gasoil fraction include additives for functional fluid formulations such as, but are not limited to, corrosion and rheology control products, emulsifiers and wetting agents, borehole stabilizers, high pressure and anti-wear additives, de- and anti-foaming agents, pour point depressants, and antioxidants.

Preferably, the other compounds comprise one or more compounds of corrosion and rheology control products, emulsifiers and wetting agents, borehole stabilizers, high pressure and anti-wear additives, de- and anti-foaming agents, pour point depressants, and antioxidants.

In another aspect, the invention provides for the use of the Fischer-Tropsch gasoil fraction in various applications. The Fischer-Tropsch gasoil fraction may be used alone or in combination with other compounds. Typically, Fischer-Tropsch gasoil fraction may be used in many areas, for instance oil and gas exploration and production, process oils, agro chemicals, process chemicals, construction industry, food and related industries, paper, textile and leather, and various household and consumer products. Other compounds that are used in combination with the Fischer-Tropsch gasoil fraction include additives for functional fluid formulations such as, but are not limited to, corrosion and rheology control products, emulsifiers and wetting agents, borehole stabilizers, high pressure and anti-wear additives, de- and anti-foaming agents, pour point depressants, and antioxidants.

Preferred applications using the Fischer-Tropsch gasoil fraction according to the present invention include, but is not limited to, drilling fluids, heating fuels or oil, lamp oil, barbeque lighters, concrete demoulding, pesticide spray oils, paints and coatings, personal care and cosmetics, consumer goods, pharmaceuticals, industrial and institutional cleaning, adhesives, inks, air fresheners, sealants, water treatment, cleaners, polishes, car dewaxers, electric discharge machining, transformer oils, process oil, process chemicals, silicone mastic, two stroke motor cycle oil, metal cleaning, dry cleaning, lubricants, metal work fluid, aluminum roll oil, explosives, chlorinated paraffins, heat setting printing inks, Timber treatment, polymer processing oils, rust prevention oils, shock absorbers, greenhouse fuels, fracturing fluids and fuel additives formulations.

In particular the invention provides the use of a Fischer-Tropsch gasoil fraction according to the invention or a fuel composition comprising such Fischer-Tropsch gasoil fraction as a heating oil.

Equally particular the invention provides the use of a Fischer-Tropsch gasoil fraction according to the invention or a fuel composition comprising such Fischer-Tropsch gasoil fraction as a lamp oil.

Still equally particular the invention provides the use of a Fischer-Tropsch gasoil fraction according to the invention or a fuel composition comprising such Fischer-Tropsch gasoil fraction as a lighter fluid, in particular barbeque lighter fluids.

The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

EXAMPLES Example 1 Preparation of a Fischer-Tropsch Gasoil Fraction Having an Initial Boiling Point of 188° C. and a Final Boiling Point of 278° C.

A Fischer-Tropsch product was prepared in a process similar to the process as described in Example VII of WO-A-9934917, using the catalyst of Example III of WO-A-9934917. The C₅+ fraction (liquid at ambient conditions) of the product thus obtained was continuously fed to a hydrocracking step (step (a)). The C₅+ fraction contained about 60 wt % C₃₀+ product. The ratio C₆₀+/C₃₀+ was about 0.55. In the hydrocracking step the fraction was contacted with a hydrocracking catalyst of Example 1 of EP-A-532118. The effluent of step (a) was continuously distilled under vacuum to give light products, fuels and a residue “R” boiling from 370° C. and above. The conversion of the product boiling above 370° C. into product boiling below 370° C. was between 45 and 55 wt %. The residue “R” was recycled to step (a). The conditions in the hydrocracking step (a) were: a fresh feed Weight Hourly Space Velocity (WHSV) of 0.8 kg/l.h, recycle feed WHSV of 0.4 kg/l.h, hydrogen gas rate=1000 Nl/kg, total pressure=40 bar, and a reactor temperature in the range of from 330° C. to 340° C.

The obtained fuels fraction (C5⁺-370° C.) was continuously distilled to give Fischer-Tropsch gasoil fraction having an initial boiling point of 188° C. and a final boiling point of 278° C. and an approximate gasoil fraction yield as shown in Table 1.

The physical properties are given in Table 2.

TABLE 1 Fischer-Tropsch gasoil fraction Yield 42 ASTM D2892 (wt. %)

TABLE 2 Fischer-Tropsch gasoil fraction Kinematic viscosity at 25° C. 2.5 According to ASTM D445 [mm²/s] content of aromatics <200 According to SMS 2728 [mg/kg] content of n-paraffins 22.9 According to GCxGC - internal testing methodology [wt. %] content of isoparaffins 74.8 According to GCxGC - internal testing methodology [wt. %] Density at 15° C. 765 According ASTM D4052 [kg/m³] T10 vol. % boiling point 207 According to ASTM D86 [° C.] T90 vol. % boiling point 259 According to ASTM D86 [° C.] Smoke point >50 [mm] Carbon number range paraffins 9-19 Flash point 74 According to ASTM D93 [° C.] content of monomethyl isoparaffins 46 According to GCxGC - internal testing methodology [wt %, based on total isoparaffins] Visual Appearance Clear and bright

Example 2

The performance of Fischer-Tropsch gasoil fraction of Example 1 as a lamp oil in a wick oil lamp has been tested.

The following resulst were observed with respect to the performance of the Fischer-Tropsch gasoil fraction of Example 1 in a lamp oil application:

-   -   (1) The flame height was nicely shaped and stable flames with no         tendency to soot under the ambient conditions.     -   (2) During burning no odor was identified.     -   (3) Upon extinguishing a candle/paraffinic like odor was         identified.

The performance of Fischer-Tropsch gasoil fraction of Example 1 as a heating fluid in a portable heater was aslo tested.

The Fischer-Tropsch gasoil fraction of Example 1 was tested as a heating fluid in a wick operated Zibro Kamin portable heater.

To reduce the chance that observations are affected by heating fluids used earlier in the heater, the former content was removed as much as reasonably possible and the sock dried with air. Subsequently the new fluid was poured into the heater's container, and the heater slightly shaken to allow air bubbles to escape.

The sock was allowed to soak in the heating fluid for 15 minutes. The following characteristics were determined:

-   (i) ease of ignition, -   (ii) odor upon ignition, -   (iii) odor during burning, -   (iv) flame characteristics during burning, -   (v) odor upon extinguishing.

The following results were observed:

-   (i) Ignition of the Fischer-Tropsch gasoil fraction of Example 1 is     easy. -   (ii) The odor upon start-up is candle/paraffinic like, and rapidly     disappears as the temperature increase in the heating section. -   (iii) No significant odor is identified during burning. -   (iv) The fluid generates heat adequately. Within 5 minutes the metal     roster of the heating element becomes red hot. -   (v) Upon extinguishing a candle/paraffinic like odor was identified,     which odor disappeared shortly after the heater was extinguished.     From the experimental results above, it can be concluded that the     Fischer-Tropsch gasoil fraction of Example 1 is highly suitable as     lamp oil or heating fluid. 

What is claimed is:
 1. Fischer-Tropsch derived gasoil fraction having an initial boiling point of at least 175° C. and a final boiling point of at most 285° C.
 2. Fischer-Tropsch derived gasoil fraction according to claim 1, having an initial boiling point of at least 180° C.
 3. Fischer-Tropsch derived gasoil fraction according to claim 1, having a final boiling point of at most 273° C.
 4. Fischer-Tropsch derived gasoil fraction according to claim 1, having a kinematic viscosity at 25° C. according to ASTM D445 from 0.8 to 1.5 cSt.
 5. Fischer-Tropsch derived gasoil fraction according to claim 1, having a flash point according to ASTM D93 of at least 45° C.
 6. Fischer-Tropsch derived gasoil fraction according to claim 1, containing no more than 4 wt % of naphthenic paraffins, based on the Fischer-Tropsch derived gasoil fraction.
 7. Fischer-Tropsch derived gasoil fraction according to claim 1, containing isoparaffins and normal paraffins in a weight ratio of isoparaffins over normal paraffins in the range of 3 to
 4. 8. Fuel composition comprising a Fischer-Tropsch derived gasoil fraction according to claim
 1. 9. A fuel composition according to claim 8, wherein the fuel composition is a heating oil.
 10. A fuel composition according to claim 8, wherein the fuel composition is a lamp oil.
 11. A fuel composition according to claim 8, wherein the fuel composition is a lighter fluid.
 12. A heating oil comprising a Fischer-Tropsch derived gasoil fraction as defined according to claim
 1. 13. A lamp oil comprising a Fischer-Tropsch derived gasoil fraction as defined according to claim
 1. 14. A lighter fluid comprising a Fischer-Tropsch derived gasoil fraction as defined according to claim
 1. 